Field of the Invention
The present invention relates to a method of manufacturing an element chip.
Description of the Related Art
Plasma etching may be used to manufacture element chips in some cases. There are wide applications of plasma etching, and for example, a method called plasma dicing for dicing a substrate is known as one of them. In plasma dicing, a substrate that has a plurality of element regions defined by a dividing region is diced into respective element chips by performing plasma etching on the dividing region from one surface to the other surface of the substrate. In such plasma dicing, only the dividing region needs to be plasma etched, that is, the element regions need to be protected from plasma. For this reason, before the plasma etching, a mask having plasma resistance is formed over the entire surface of the substrate, and then a part of the mask located in the dividing region is removed while leaving parts of the mask located in the element regions, thereby forming a finalized mask for plasma etching in each necessary region. At the same time, patterning is also performed to cut parts of a protective film or a layer thereunder in the dividing region by laser machining or the like. In this way, the regions to be plasma etched are defined, and consequently accurate plasma dicing is performed (see, for example, U.S. Pat. No. 8,703,581).
When plasma dicing is performed on a substrate with a metal layer, a process (laser grooving process) for providing grooves is applied to a protective film and the metal layer thereunder, which are patterned. During this process, processing waste called debris, generated by an ablation phenomenon, may often be scattered. Most of the scattered debris can be removed by plasma cleaning or the like in a later step, but some of the debris having a large particle size remain without being removed, which may deteriorate the reliability and yield of a device.